1 Introduction
The global public terrain data include: GTOPO30-DEM, ASTER-GDEM, SRTM90, ALOS-AW3D30, etc. Other global terrain data such as World DEM and ALOS-AW3D (5m resolution) cannot be obtained for free.
SRTM: NASA and the National Geospatial-Intelligence Agency (NGA) used the "Endeavour" space shuttle launched in February 2000 for a total of 11 days. Through the technical means of multi-band radar interferometry, it obtained approximately Topographic data for 80% of the world's land area. The current public version of the SRTM grid has a size of about 90m. The officially announced elevation accuracy is better than 16m, and the plane accuracy is better than 20m. The coordinate reference system is WGS84, and the elevation datum is EGM96 geoid.
ASTER-GDEM: jointly produced by NASA and METI of Japan’s Ministry of Economy, Trade and Industry using global optical stereoscopic images, it was released in June 2009 and covers the area between north and south latitudes of 83° around the world. The grid interval is about 30m, and the nominal The elevation accuracy is about 20m, and the plane accuracy is about 30m.
ALOS-AW3D30: The Japan Aerospace Exploration Agency (JAXA) used the PRISM image of the panchromatic three-view stereo observation sensor on the ALOS satellite to perform stereo surveying and mapping, and was released in May 2016. The grid interval is about 30m, the nominal absolute elevation accuracy is 5m, and the plane accuracy is about 15m. However, AW3D30 terrain data has gaps in some areas, and SRTM90-DEM needs to be selected as a supplement. In high latitude areas, it can also be replaced by low-precision ASTER-GDEM or GTOPO30-DEM.
2 Data download
2.1 ALOS-AW3D30 Download
Step 1
Open the registration page, http://www.eorc.jaxa.jp/ALOS/en/aw3d30/registration.htm. Fill in the relevant information.
Step 2
A confirmation letter will be sent to the mailbox. After confirming your registration, you will receive another email providing your login and password.
Step 3
Open the download URL and log in: http://www.eorc.jaxa.jp/ALOS/en/aw3d30/data/index.htm
After logging in to the download page, click the required data location on the map to download the data file of 1×1 degree or 5×5 degree. The downloaded file format is a tar.gz compressed package. The format of DSM data files is GeoTIFF.
Check the downloaded data resolution in ENVI, you can see that it is 30m resolution. The unit is degrees, roughly converted to meters is about 30 meters.
2.2 SRTM data download
2.2.1 Method 1
Step 1:
Open the link ( https://earthexplorer.usgs.gov/ ) and log in to your account.
Step 2:
(1) Set the area, time (sometimes there will be no data if the time is set), etc.
(2) Select the DEM data, click Results and wait for the data to be generated
(3) Download
2.2.2 Method 2
To download in EarthData, just search for SRTM, which is very convenient. Link: https://search.earthdata.nasa.gov/search .
reference
[1] AW3D30 DSM data download
[2] SRTM data introduction and download